Pardon my French: Please excuse me for swearing. Used as a way to apologize for using profanity (bad words) or for saying something that may offend another person.
Pardon my French, but that dress does NOT look good on you.
An early example of the phrase was in The Lady’s Magazine from 1830, in which the speaker used a French word to insult someone:
Bless me, how fat you are grown! – absolutely as round as a ball: – you will soon be as enbon-point (excuse my French) as your poor dear father, the major.
“Enbon-point” is a French word for plump (fat). The phrase was later popularized in the 20th century in Michael Harrison’s All Trees were Green, 1936.